Conventional methods of softening fabrics are focused on rinse added fabric softening liquids and dryer added sheets. Conventional fabric softening compounds include cationic quaternary ammonium compounds (cationic “quats”) having two symmetrical alkyl or alkenyl chains with an average carbon chain length of from 12 to 18, for example, amido imidazolinium compounds. Examples of attempts to provide softening benefits during the rinsing process are described in: U.S. Pat. No. 5,919,751 to Bird et al., U.S. Pat. No. 5,490,944 to Suazon et al., and U.S. Pat. No. 4,569,800 to Stanley et al.
Softening-through-the-wash compositions (hereinafter “STW” compositions) have become popular as they provide consumers the ability to soften fabrics during the wash, without waiting for the rinse process or the dryer process. Attempts to incorporate conventional cationic quats into STW compositions have encountered problems such as the undesirable formation of water insoluble flocs, also called precipitates. These water insoluble flocs are the result of the ion pairs formed from the conventional cationic quats with the anionic surfactants of the detergent and are known to cause composition opacity and undesirable appearance on the shelf (i.e., phase split). Moreover, these flocs can leave residues on laundered fabrics and cause stains.
Multi-compartment unitized dose pouches have been used to separate the conventional cationic quats from the anionic surfactants. Although the formation of insoluble flocs in the packaged product is minimized, this approach does not resolve the problem of the incompatibility of the quat and anionic surfactant; for example, flocs can still form in the wash bath. Examples of attempts to use multi-compartment unitized dose pouches for STW purposes are mentioned in: U.S. Pat. No. 6,291,421 to Alain et al. and U.S. Pat. No. 6,110,886 to Scepanski et al.; and U.S. Patent Publ. Nos. 2007/0105739 A1 and 2005/0020476 A1, both to Wahl et al.
Recent attempts to address the incompatibility problems with these ingredients involve the use of mono-alkyl quats. While mono-alky quats are less likely to form insoluble flocs in the presence of anionic surfactants, mono-alkyl quats are rather expensive and are believed to be inferior to conventional cationic quats having two alkyl chains, with respect to softening and antistatic benefits. See U.S. Pat. No. 5,466,394 to de Buzzaccarini et al., U.S. Patent Publ. No. 2005/0164905 to Chawla et al., and WO 2006/072083 to Lin et al. Thus there remains an ongoing search for improved STW formulations which provide effective deposition of a fabric conditioning active on the treated fabrics, providing desirable fabric conditioning benefits including but not limited to softening, anti-static, and anti-microbial benefits.